Oral administration is the most preferred and convenient route of administration for various types of drugs. However, there are certain drugs that do not have uniform absorption throughout the entire gastrointestinal tract and are predominantly absorbed from the stomach and the upper part of the intestine. For such drugs, it is beneficial to develop oral gastroretentive dosage forms that can remain in the gastric region for longer periods of time so as to significantly prolong the gastric retention time. Such gastroretentive dosage forms are also useful for drugs that are poorly soluble, degraded by the higher pH of the intestine, or have an absorption which is modified by changes in gastric emptying time. Gastroretentive dosage forms are also useful for local as well as sustained drug delivery for certain disease states.
To formulate such stomach-specific gastroretentive dosage forms, several techniques have been described in the prior art such as hydrodynamically balanced systems (HBS)/floating drug delivery system, low density systems, bioadhesive or mucoadhesive systems, high density systems, superporous hydrogels, and magnetic systems.
U.S. Publication No. 2007/0269511 discloses a pregabalin gastroretentive formulation comprising a matrix forming agent and a swelling agent wherein the matrix forming agent is polyvinyl acetate and polyvinylpyrrolidone, and the swelling agent is cross-linked polyvinylpyrrolidone.
PCT Publication No. WO 2011/151708 discloses a gastroretentive dosage form comprising a GABA analog, at least one swelling agent, at least one non-swelling release retardant, and at least one pharmaceutically acceptable excipient.
U.S. Publication No. 2011/0135723 discloses once-daily pharmaceutical compositions of pregabalin wherein the excipients include one or more water-insoluble components or a combination of one or more water-insoluble components and one or more water-soluble components.
U.S. Publication No. 2010/0255067 discloses pharmaceutical compositions comprising pregabalin, a hydrophobic release-controlling agent, and other pharmaceutically acceptable excipients.
PCT Publication No. WO 03/035029 discloses a gastric retentive dosage form consisting of single polymer matrix comprising an active agent and hydrophilic polymers such as hydroxypropyl methylcellulose and poly(ethylene oxide). U.S. Pat. No. 6,207,197 discloses gastro-retentive controlled-release compositions comprising microspheres containing a drug in an inner core, a rate-controlling layer of a hydrophilic polymer, and an outer layer of bioadhesive cationic polymer.
However, administration of such dosage forms might result in fluctuating drug levels in the plasma. In order to overcome this drawback, the inventors have now developed an osmotic floating tablet comprising: (i) an inner core comprising a drug, one or more low density polymers, and one or more pharmaceutically acceptable excipients; and (ii) an outer osmotic coating surrounding the inner core that is substantially permeable to the surrounding fluids and substantially impermeable to the drug. The incorporation of such an osmotic coating on the floating inner core provides several advantages over conventional gastroretentive dosage forms, such as reduction in the plasma level fluctuations, zero order drug release, and resistance against alcohol-induced dose dumping.